Bernina 707 Cam removal

Hello, my wife's Bernina 707 stops halfway through a complete revolution of the pattern cam. I notice that there is a split in it, which I think causes the machine to seize during a complete cycle of the cam. It can only be freed manually, this lasts only a few seconds. I would like to remove the cam and replace it. There seems to be a shaft pin keeping it in place, the face of the pin is accessible on the back of the machine. Should this be hammered so it goes back into the machine in order to remove the cam? Of course I need to ensure I do not damage the machine in the process otherwise life will be hell and I will never stop hearing about it. Then I will have to emigrate and that is expensive.

1 Answer

Take off the black metal bit that is above the pattern cam (4 screws). beneath you see 2 small screws, inside the metal frame, on each side of pattern cam. Take them out. Spin the pattern cam until you see one screw in the cam itself. Take that out too. Now you can push the splint out which holds the cam.

This was the best information and guidance that I found, I followed instructions exactly and my machine works just fine. Thank you so much for this answer!This was the best information and guidance that I found, I followed instructions exactly and my machine works just fine. Thank you so much for this answer!

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Related Questions:

This series are prone to cracking the cam gear. Search Bernina cam gear at www.ashleyandthenoisemakers.com and there is a full example with pictures on how to do it. Try ebay for the gear. Check prices.

1. The switching pawl (lever on the top cover that switches from zigzag to cam patterns) may be engaged in the cam or automatic pattern side. Check that first.
For zigzag application, the lever must be engaged in the zigzag side (lever pulled back toward the operator). The stitch width dial is then used to provide your choice of width.
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2. It is common, due to oil varnishes, that the switching pawl that is actuated by this lever is stuck between the zigzag and the automatic position, thus preventing the transmission of power to either the zigzag cam or the automatic pattern cams and to the needle.
The best way to detect this is to remove the top cover. You can then switch the lever back and forth to observe if the switching pawl engages firmly into either of the receiving forks. If the switching pawl is sticking, a few drops of certain solvents are applied by a technician on the switching pawl support. The switch lever can be rapidly switched back and forth until you see the switching pawl engage into the receiving forks and you hear a crisp clicking during each engagement. This repair can be permanent or it may create only a temporary fix due to the amount of oil varnishes on the parts.
If the machine is heavily varnished, it suggested that the parts be disassembled and cleaned for flawless performance. If the machine had been sprayed with WD-40, petroleum based solvents like mineral spirits will not break down these varnishes.
A caution regarding solvents...DO NOT USE (WD-40) as your solvent. WD-40 is a marvelous product for its intended application as a water displacement device. It is not to be used for lubricating a sewing machine. Note: "Bernina Technical Information bulletin #1" issued in 1982, forbade the use of such spray lubricants and solvents. SewTechnical Home

We are assuming that the zigzag width dial is at the widest position but the needle will not move laterally for zigzag... The following logic should be applied for Bernina machines 530, 730, 830, 930 machines with a guided motion zigzag cam.
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1. The switching pawl (lever on the top cover that switches from zigzag to cam patterns) may be engaged in the cam or automatic pattern side. Check that first.
For zigzag application, the lever must be engaged in the zigzag side (lever pulled back toward the operator). The stitch width dial is then used to provide your choice of width.
----------------------
2. It is common, due to oil varnishes, that the switching pawl that is actuated by this lever is stuck between the zigzag and the automatic position, thus preventing the transmission of power to either the zigzag cam or the automatic pattern cams and to the needle.
The best way to detect this is to remove the top cover. You can then switch the lever back and forth to observe if the switching pawl engages firmly into either of the receiving forks. If the switching pawl is sticking, a few drops of certain solvents are applied by a technician on the switching pawl support. The switch lever can be rapidly switched back and forth until you see the switching pawl engage into the receiving forks and you hear a crisp clicking during each engagement. This repair can be permanent or it may create only a temporary fix due to the amount of oil varnishes on the parts.
If the machine is heavily varnished, it suggested that the parts be disassembled and cleaned for flawless performance. If the machine had been sprayed with WD-40, petroleum based solvents like mineral spirits will not break down these varnishes.
A caution regarding solvents...DO NOT USE (WD-40) as your solvent. WD-40 is a marvelous product for its intended application as a water displacement device. It is not to be used for lubricating a sewing machine. Note: "Bernina Technical Information bulletin #1" issued in 1982, forbade the use of such spray lubricants and solvents. SewTechnical Home

I don't know what a stitch cog is by your definition but I suspect that you may be referring to the cam stack worm gear, part # 310 007 03. These gears are available, however those produced and sold as after market parts online have ranged from bad to very bad. I would suggest that you find an OEM part (not a reproduction) that are still available from time to time on EBAY etc.
Changing the gear is not as straight forward as it may look. The proper replacement requires: 1. removal of the cam stack without damaging the machine parts, 2. removal and installation of the new gear with the correct alignment of the individual cams, 3. installation of the cam stack and pattern indicator without axial play, 4. correct parabola timing of the main-shaft worm wheel and cam stack gear, 5. synchronization of the zigzag and automatic cam parabolas, 6. pattern indicator timing, 7. checking and adjusting the automatic needle position. SewTechnical Home

Dodo,
Too many specialty tools needed to make such repairs.
Leave these and other such repairs to a professional trained and authorized trained and certified technicians.
Cheers,
Kelly
San Diego, CA
Embroidery Services

Have you been oiling the bearings per the guide? Try to isolate the upper mechanism versus the lower by rocking the handwheel and observing which causes the bind (take the bobbin and needle thread off to prevent jamming). You may have to remove some of the covers to see most of it. As long as no gearing becomes shifted or uncoupled, you should not cause trouble. Try taking the motor belt off to see if the motor itself may be binding. Good to see people keeping old, but still working machines running

If you are selecting patterns but only getting a straight stitch after making sure you have set the width, there may be a chance that the pattern camstack has split and the selector finger is stuck in the split, more common than people think,
take the top off the machine and check

Check to see if the cam stack gear does not have a crack in it. The other problem is the cam engager lever is does not engage the cam stitches because it is gummy. To solve this, lift the lid and follow the lever to where it make contact, add a penetrant oil. More the lever back and forth as fast as you can and work the penetrating oil into the area. It should click back and forth and snap between the back and front V's. One is for the zig zag and straight stitches and the other is for all cam patterns. Once it is clicking and snapping back add regular oil. Thensew out your pattern stitches. If the machine binds then you could have a cracked cam stack gear and has to be change by a Bernina service center.
SewTechnologist